The allergen-specific IgE antibody to total serum IgE ratio is a key variable being investigated in relation to[unreadable] allergic symptom induction in this Program Project. The Diagnostic Core will conduct two main activities. In[unreadable] Aims 1 and 2, the Diagnostic Core will provide a service function in which analytical measurements will be[unreadable] performed on serum, cells, tissues, and lavage fluids collected on subjects in the project using validated assays.[unreadable] In Aims 3 and 4, the Diagnostic Core will investigate several hypotheses fundamental to improving the analytical[unreadable] sensitivity of allergen-specific IgE assays and validating the accuracy of the total and "free" (non-Omalizumab[unreadable] bound) total and allergen-specific IgE assays. More specifically, in Aim 1, the Diagnostic Core will provide state-of-[unreadable] the-art serologic, immunohistology, in situ hybridization, mediator and cytokine, nasal lavage chemistries and[unreadable] aeroallergen testing on specimens collected during recruitment and the longitudinal monitoring phases of the[unreadable] studies. Serologic testing (total and allergen-specific IgE, tryptase), nasal lavage chemistries, immunohistology,[unreadable] in situ hybridization, aeroallergen (Pel d 1) and cat extract validation will be performed in or under the auspices[unreadable] of the CLIA-88 certified Johns Hopkins Dermatology Allergy and Clinical Immunology (DACI) Reference[unreadable] Laboratory. In Aim 2, The Diagnostic Core Group will quantify "free" (non-Omalizumab bound) total IgE[unreadable] measurements in serum of subjects who have received Omalizumab to reduce free IgE levels, using our newly[unreadable] developed immunoenzymetric assay. A free allergen-specific IgE antibody assay will also be developed and[unreadable] configured on the ImmunoCAP platform to permit free specific to total IgE ratios to be computed. Aim 3 will[unreadable] investigate the hypothesis that 1 nanogram of allergen-specific IgE antibody as measured in a 3rd generation[unreadable] FDA-cleared assay equals 1 nanogram of total serum IgE. Verification of this quantitative relationship is critical[unreadable] to the accurate measurement of the specific to total IgE ratio. Aim 4 will investigate the hypothesis that the[unreadable] allergen-specific to total serum IgE ratio in allergic subjects before treatment with an IgE lowering drug[unreadable] (Omalizumab) remains constant for months during and following treatment, despite a expected many fold[unreadable] increase in total serum IgE. It is anticipated that Aims 3 and 4 will be completed within year 1 of the program so[unreadable] that free specific to total IgE ratio measurements will be available to investigations conducted in the 3 projects in[unreadable] this program.[unreadable]